Stage processes absorption

Nuclear reactions induced by electromagnetic radiation can be described - at least for sufficiently low-photon energies - in terms of a two-stage process. Absorption of a photon leads to an intermediate highly excited state of the nucleus. The excitation energy of this so-called compound nucleus can then be released by emission of photons, neutrons, or charged particles. 

It is essentially a 2-stage process, as shown in Figure 3-5. First, there is a dissociation (dissolution) of particles then the dissolved molecules or ions diffuse across capillary walls and are taken up by the blood. Immediately following dissolution, rapid absorption is observed. For some elements, rapid absorption does not occur because of binding to respiratory-tract components. In the absence of specific data for specific compounds, the model uses the following default absorption rate values for those specific compounds that are classified as Types F (fast), M (medium), S (slow), and V (instantaneous) ... 

Though packed absorption and stripping columns can also be designed as staged process, it is usually more convenient to use the integrated form of the differential equations set up by considering the rates of mass transfer at a point in the column. The derivation of these equations is given in Volume 2, Chapter 12. 

Mass transfer in packed columns is a continuous, differential, process, so the transfer unit method should be used to determine the column height, as used in absorption see Section 11.14.2. However, it often convenient to treat them as staged processes and use the HETS for the packing employed. For random packings the HETS will, typically, range from 0.5 to 1.5 m, depending on the type and size of packing used. 

Sherwood, T. K. and Pigford, R. L. Absorption and Extraction (McGraw-Hill Book Co., New York, 1952). Sherwood, T. K., Pigford, R. L. and Wilke, C. R. Mass Transfer (McGraw-Hill Book Co., New York, 1975). Smith, B. D. Design of Equilibrium Stage Processes (McGraw-Hill Book Co., New York, 1963). 

Fluorescence is a three-stage process excitation via the absorption of a radiation, excited state for a very short time -(10 9 sec), and emission. The excitation of a molecule is achieved by the absorption of a light quantum of an appropriate wavelength, promoting, in a simplified view, a ir or nonbonding (n) electron to a 7r antibonding orbital. The quantum yield is a fundamental molecular property that describes the ratio of the number of emitted photons to the number of photons absorbed. 

The process features of carbon dioxide triple-point crystallization and slurry absorption of carbon dioxide have been demonstrated with the first generation bench-scale apparatus. Current efforts are focused on the design and construction of an improved version of the carbon dioxide triple-point crystallizer in cooperation with the U S Department of Energy. Future efforts are planned to design and construct absorption units to study multi-stage slurry absorption of carbon dioxide, and the more conventional gas-liquid absorption of sulfuruous compounds with liquid carbon dioxide. 

The overall removal process would consist of two stages the absorption stage, in which the sorbent is converted to the sulfide form by its reaction with the H2S in the feed gas, and the regeneration stage, wherein the sulfide is converted to an oxide. It thus represents a cyclic process. Fixed-bed, moving-bed and fluidized-bed operations have been considered for the purpose. Kinetic data are necessary for choosing a proper reactor type and for the design... 

In the following, the principles of mass-transfer separation processes will be outlined first. Details of mass-transfer calculations will be introduced next and examples will be given of both equilibrium-stage processes and diffusional rate processes. The chapter will then conclude with a detailed discussion of the two single most applied mass-transfer processes in the chemical industries, namely distillation and absorption. 

Multiple equilibrium stage processes simulated in this program are distillation, absorption, and stripping. Both simple and reboiled absorbers are included, and multiple feed plus side-stream products are possible from the fractionators. Matrix- and short-cut-type solution methods are provided in separate subroutines. 

The process for absorbing acid gas takes place in two stages (1) absorption and (2) regeneration. The absorption takes place in a column where the sour gas is contacted with the lean solvent. The rich solvent is sent to a second column where the solvent is regenerated. Heat is applied to the system via a reboiler and the overheads are condensed, typically in an aerial cooler. The solvent regeneration is done not only at higher temperature, but also at lower pressure. Figure 1.1 is a schematic of the process. 

Where selective H2S removal is required, together with deep C02 removal, two absorption and regeneration columns may be required essentially in a two-stage process, as illustrated in Figure 5.25.195 H2S is selectively removed in the first column by a lean solvent that has been deeply stripped with steam, while C02 is removed, from the now H2S-free gas, in the second absorber. The second-stage solvent can be regenerated with air or nitrogen if very deep C02 removal is required.189... 

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